At present, there already exist cards which are encoded with a pattern out of an electrically conductive layer in order to make them readable by means of a capacitive multi-touch sensor.
In WO 2010/051802 for instance, an information carrier is disclosed, comprising an electrically non-conductive substrate, an electrically non-conductive adhesive layer and an electrically conductive information layer. Furthermore, at least another layer is arranged which covers at least the area of the substrate with the structured information layer.
In WO 2011/154524, an information carrier is disclosed comprising a substrate with at least one layer which is applied area-wise and electrically conductive, with the layer being the touch structure. This touch structure comprises at least one conductive trace, a coupling surface and/or a touch point. On the substrate and the electrically conductive touch structure, at least one cover layer is situated in order to cover the touch structure not to damage it and to make it invisible.
Known cards having a predetermined pattern of an electrically conductive material all suffer from the drawback that, when on the electrically conductive pattern which is applied on the substrate of the card, a covering layer is applied, on the places where this covering layer covers the pattern of conductive material, a colour difference in this covering layer can be observed. The colour of this covering layer is thus uneven, which is not at all desirable. When for instance a white covering layer is applied over the substrate and over the electrically conductive pattern, the white does not appear evenly white on the places where this electrically conductive pattern is situated.
The problem underlying the invention puts himself with different colours of the electrically non-conductive covering layers. This problem especially occurs when said electrically non-conductive covering layer comprises a white covering layer which is applied on said electrically non-conductive substrate and said first predetermined pattern of electrically conductive material.
The problem underlying the invention furthermore also puts himself with different application techniques of this electrically non-conductive layer. This problem especially occurs when the electrically non-conductive covering layer is printed over the first predetermined pattern of electrically conductive material, especially when being digitally printed, since printing ink by definition is transparent and covering varnishes never cover for 100%. This problem however can also occur when a thin covering layer, for instance a thin paper layer, is laminated on said substrate and said first predetermined pattern of electrically conductive material.
A man skilled in the art being faced with this problem in the field of printing inks will have the normal reflex to apply several covering layers or a more opaque layer over the substrate and the electrically conductive pattern in order to ameliorate the colour difference in this covering layer. This solution however will not solve the problem underlying the invention.
There consequently exists the need to solve this problem.